ES2374544T3 - PROCEDURE FOR PLANNING THE SPEED OF A SHIP ALONG A ROUTE. - Google Patents

Abstract

A method for planning the velocity of a craft along a predetermined route, where said method comprises the step of transforming demands and limitations of said route and said craft into a time-distance domain. Said planning subsequently takes place in said domain. The method saves computational time.

Description

Procedure for planning the speed of a ship along a route

Field of the Invention

The present invention relates to a method and a system for planning the speed of a vehicle along a predetermined route.

Background

Mission planning is an important activity for both manned and unmanned ships. Such planning provides a means to increase the security of a mission, and also enables the maintenance of a schedule. Mission planning is a process that is briefly described as the activity necessary to find a route between two landmarks.

A number of restrictions can be imposed on the route. For example, the aforementioned route should avoid threats

or static and dynamic ships, minimize fuel consumption, stay within predetermined space limits in terms of flight level and position, reach the target at a certain time, have a certain speed and a certain course . The route must also be such that the ship can move along the said route taking into account the physical properties of the said ship in terms of performance in speed, acceleration and maneuverability.

It is possible to use pure analysis to describe the objective and constraints as a major optimization problem, and then apply techniques that can find a route that solves the problem. Actually, this is difficult, since it requires large amounts of computing power to solve a real problem.

The most advanced techniques include dividing the problem into several steps, which makes it possible to plan in "real time". First, the route is planned, regardless of the speed and then the speed is planned along the given route.

Prior art

US 6,061,612 discloses a flight management system for ships, which includes a process for managing the aerodynamic speed of an aircraft in flight. The procedure includes a first step to determine a point on the flight path where it is theoretically possible to comply with a required time constraint, following a preset speed profile. In a second step, the speed is calculated and a new speed profile is determined. This is obtained by determining the speed corrections segment by segment, from the point to the last modifiable segment. The speed change in each segment is limited to a maximum value. The new velocity is calculated on the basis of the curve that shows the flight time t as a function of the velocity V. This curve can be approximated by a curve that satisfies an equation with three coefficients (C1, C2, C3):

V = C1 / t + C2 / t2 + C3 / t3

Compliance with time constraints is guaranteed by this procedure, while the requirements of the pilot and air traffic controllers are met.

US 4,774,670 also discloses a flight management system, comprising a system that can accept flight data information, including the required arrival time.

US 6,507,782 discloses an aircraft control system to reach a reference point at a required arrival time.

US 5,408,413 discloses an apparatus and a procedure for controlling an optimization calculation of aircraft performance to achieve restricted time navigation.

US 5,121,325 discloses a system of control of the required arrival time.

US 6,266,610 discloses a multi-dimensional route optimizer.

Summary of the invention

The problem of speed planning, or of speeds, over a distance that has already been planned, is relatively simple to solve, calculating the average speed along the distance. The problem becomes more complex when it is necessary to take into account other moving objects and other restrictions, as well as limit values. These requirements and limitations include:

Threats and moving (dynamic) objects that cross the planned route, as far as possible, will be avoided.

the speeds at the beginning and at the end of the route, specified by the mission, and the time or time window, in which the ship must pass the end point of the route.

ship performance, including maximum and minimum speed, acceleration and deceleration.

the shape of the route in relation to the turning performance of the ship, that is, an estimated maximum speed along a certain part of the distance, for example, a closed curve, so that the ship can follow the route within a certain error.

The object of the invention is to provide a general procedure for solving the problem mentioned above, so that a permitted speed for the planned route can be calculated, which satisfies the conditions. There does not appear to be an existing solution that manages the restrictions mentioned above in a simple way. The present invention solves the problem mentioned above by handling the restrictions of the problem in such a way that the problem can be transformed. When the problem has been transformed, conventional procedures can be used to solve it. The invention provides a method for planning the speed of a ship along a pre-established route, according to claim 1.

The invention also provides a system for carrying out the planning according to the procedure, and a corresponding computer software product.

Brief description of the drawings

Figure 1 shows, in the form of a pseudo-flow chart, a scheme of a speed planning procedure along a route.

Figure 2 shows an example of a speed planning problem for a route between locations A and B in a map representation.

Figure 3 shows a representation of the problem in Figure 2 in the time-distance domain.

Figure 4 shows an additional aspect of the problem of Figure 2.

Figure 5 shows the representation in the time - distance domain of the problem of Figure 4.

Figure 6 shows an additional aspect of the problem of Figure 4.

Figure 7 shows the representation in the time - distance domain of the problem in Figure 6.

Figure 8 shows a solution in the time-distance domain of the problem of Figure 7.

Figure 9 shows a solution in the time - distance domain of a problem in multiple sections.

Figure 10 shows a velocity profile of the problem of Figure 8.

Detailed description of preferred embodiments

Figure 1 shows, in the form of a pseudo-flow chart, a scheme of a speed planning procedure along a route. The data representative of the demands of the mission 105, the dynamic limitation of the ship 100, the route 115, and the image 120 of the dynamic situation are fed to a transformation and construction unit 125. The information regarding the image 120 of the dynamic situation is fed by means of a prediction unit 130. The transformation and construction unit transforms the incoming data in the time-distance domain, so that it fits into a time-distance space and / or a Time - distance graph. The transformation and construction unit additionally establishes the problem, that is, all the limitations and restrictions, in the time-distance space and therefore constructs a static problem 135. The said static problem 135 is then solved with the help of a search and optimization unit 140. The output of said search and optimization unit 140 comprises a route, including the planned speed for the route.

Figure 2 shows an example of a route between locations A and B. In a first step, the route is planned with reference to the terrain and static threats. The aircraft that has an intersection course is not considered in this first step. It is considered that a route 230 has been planned between locations A and B. An area of terrain obstacles 205 and a static threat 210 represent restriction areas of route 230, that is, route 230 must not pass through the said areas 205, 210. Now it remains to be determined the velocity V for route 230, such that the ship arrives at location B at a specific time of time T. When studying a distance of route 230 and the restrictions imposed by the required arrival time T, it is possible to trace the dynamic limitations of the ship and the restrictions of route limits in a figure that shows how far the ship can stay in the distance and still reach B at time T, see figure 3.

Figure 3 shows a time-distance representation in a representation of the map in Figure 2. The upper limitation line 310 corresponds to the possibility of starting the trip at the highest possible speed and then changing to a minimum speed. The lower limit line 320 corresponds to the opposite - start with a minimum speed and then change to a maximum speed. Together, the two limiting lines 310, 320 create a distance envelope, which describes the distances that can be reached at a certain time and that meet the dynamic demands and constraints. The average D / T speed is described by the straight diagonal line 330. On the stage there is also an aircraft 220, which represents a dynamic threat on a course 240 that intersects planned route 230. When predicting the position of threat 220 plus forward in time, the moment in time when the threat coincides with route 230 at an intersection point 410, see figure 4. In this example, this will happen at a time in which t is equal at 550 seconds

The dynamic threat is described in the distance envelope as a static curve, the shape of which depends on the predicted position and the uncertainty of the predicted position of the threat. A threat envelope is drawn that circumscribes the curve, corresponding to the maximum and minimum speeds, which then describes the distance and time at which it cannot be guaranteed that the collision is avoided. The distance envelope, including the threat envelope, is described in Figure 5.

Figure 5 shows the static representation of the dynamic threat of Figure 4. If the ship passes through threat 510, there is a risk of collision, and this would be the case if the average speed for the entire route, that is, diagonal line 330 would have been selected. In the scenario it can also be seen, as shown in Figure 6, that a sharp turn 605 is present in the planned route. Such a turn implies that a restriction relative to the maximum speed has to be introduced along a portion 605 of the route. Because the maximum speed was used to determine the distance envelope, the envelope mentioned, of course, must be reviewed.

In Fig. 7, the distance with a reduced speed is marked by two horizontal lines 710, 720, and the upper curve is received with a somewhat suppressed shape 730, 740, 750 compared to the straight original line representing the maximum speed 312 The limitation of this speed is valid at all times, which can also influence the lower curve and the threats in this area. By projecting the planned route with respect to mission time restrictions and adding additional restrictions due to the ship's performance, dynamic threats and route limitations in terms of maximum speed, Create a static description of the problem. Speed restrictions may also occur if the flight altitude varies along the route.

Therefore, the problem has now been transformed into the time - distance domain.

Speed planning

The problem now is to find, in the time-distance domain, a path from beginning to end that remains within the envelope and does not pass through the threat. This is the same problem that had to be solved in the route planning, but with the difference that it is planned here in other dimensions. Valid search addresses are limited by ship speed, acceleration and limitations on maximum and minimum speed in certain portions of the route.

It is also possible to use different tactics when the speed has been planned, for example, a) approach the average speed as much as possible, or b) fly with a fuel economy speed as much as possible, or c) maximize the freedom of maneuver of such that new threats can be avoided when the ship has traveled a part of the distance. The required tactics can be added to the planning algorithm, so that the correct behavior is obtained.

Figure 8 shows the result when the speed is planned along the route described above. In this particular case, the number of intermediate nodes (points with speed change) have been reduced to one. The planned speed 820, 830 implies that a higher initial speed is maintained, so that the route point of the intersection with the threat is passed before the threat arrives. Figure 10 shows the velocity profile as determined by the derivative with respect to the time of the distance profile in Figure 8.

Sequence of distance envelopes

A mission often comprises several sections, in which each section ends at a point in the mission that has temporary restrictions. The restrictions vary, from the requirement that the ship must pass through the point at a given time, to the requirement that the ship must pass through the point within a given time window, until there are no time restrictions. By means of the union of the sequences of the different envelopes of distances of sections, without difficult time requirements, it is possible to realize a planning of the speed of many sections simultaneously. The purpose of this is to see the whole, and create a prerequisite as good as possible to subsequently meet the time constraints present in the mission.

Figure 9 describes two envelopes of distances of two adjacent sections in the mission of the example. The first section 910 has a time window 930 as a restriction at the point of arrival, and the second section 920 has a fixed time restriction, that is, a specific time that must be met. By using the time window 930, a more uniform speed can be planned than would be the case if two average speeds were used along the distance. Also in this case it is possible to use different tactics to optimize the choice of speed along the route. As an example, it can be mentioned that something could happen along the route, which could require the route to be re-planned. This with almost all

5 security would result in a longer route than the original, so it may be practical to initially maintain a higher speed to gain ground as soon as possible.

Advantages

The procedure described above solves the problem of speed planning in a general way. Regardless of the existence of dynamic ships or threats that can cross the route, or

10 If there are speed limitations along the distance, the speed is planned considering the requirements of the mission and the dynamic limitations of the ship.

The strength of this procedure is that the planning is done on a "map" time-dependent, which makes all dynamic aspects static during the same planning. Therefore, it is possible to use conventional algorithms for route planning to solve the problem.

15 The procedure can be used as a component in vehicle planning, navigation or control devices (on board or off-board) to determine speeds along a route, for example at vehicle control stations Unmanned aerial vehicles (UAVs), aircraft flight management systems, air traffic control stations, ship navigation systems, etc. The procedure is equally useful for all types of vehicles and ships (land, water and air).

Claims (3)

1. A procedure implemented in a computer system for planning the speed of a ship along a predetermined route, comprising the following steps:

 -

obtain data representative of the demands of the mission;

 -

obtain data representative of the dynamic limitations of the ship;

 -

obtain data representative of a predetermined route;

 -

obtain data representative of an image of the dynamic situation;

-

transform the aforementioned mission demand data, dynamic limitation data, route data and dynamic situation data in the time - distance domain;

-

create a distance envelope (310, 320) in said time-distance domain;

-

determine a distance profile in the time - distance domain that is maintained within the distance envelope (310, 320); determine a velocity profile from the derivative of the distance profile,

wherein the stage of creating a distance envelope comprises the creation of an upper limit curve (310) and the creation of a lower limit curve (320) in which said stage of creating an upper limit curve (310 ) includes the stage of create a time-distance curve, or the equivalent of such a curve, corresponding to the case in which the ship initially travels at maximum speed and changes to the minimum speed at the last moment to reach a point of arrival at the earliest arrival time allowed, and wherein said step of creating a lower limit curve (320) comprises the step of

-

create a distance-time curve, or an equivalent of such a curve, which corresponds to a case in which the ship initially travels at the minimum speed and changes to the maximum speed at the last moment to reach a point of arrival at the last allowed arrival time,

 The method also includes the stage of creating a threat envelope (520, 530), and in which said determination of a velocity profile includes the stage of creating a distance time curve, representative of said velocity profile, that does not cross the area defined by the threat envelope, and in which the dynamic situation data includes data from objects that intersect the predetermined route, including the estimated course and speed, and variations in speed and / or uncertainty , and in which the threat envelope is created by creating an upper limit (520) and lower limit (530) curve for the object of the threat, in a manner similar to that described for the ship using the data of dynamic situation.

2.

A system configured to plan the speed of a ship along a predetermined route according to the procedure of claim 1.

3.

A computer software product for executing the method of claim 1.